To facilitate an understanding of the invention, a brief description of a typical use environment for an adjustment device in a rotary tool follows: Rotary cutting tools have a generally cylindrical tool body. One or more cutting inserts are generally secured around the periphery of the tool body in recesses known as pockets that provide a seating surface or surfaces that support the insert. Each insert is secured into its respective pocket by retaining devices, such as wedges, clamps, screws or combinations of these devices. While pockets and retaining devices secure the inserts during use, they do not provide means for making fine adjustments in the position of the cutting edges of the inserts with respect to each other or the tool body.
Fine adjustment of cutting edge position is desirable since even minor misalignment, of as little as about 0.001 inches, between the edges of the several cutting inserts can result in surface imperfections on the surface generated during machining. Variables in the size and shape of pockets in the tool body may cause such misalignment. Additionally, the size and shape of the inserts can vary 0.001 inches or more due to manufacturing tolerances or uneven wear during use. Thus, there is a demand in the industry for cutting tools that provide for small adjustments in the position of inserts in the tool body to improve alignment of the inserts' cutting edges relative to the tool body and the other cutting edges.
In the prior art there are known cutting tools, for instance adjustable reamers, that use screws with tapered heads for adjusting cutting elements through secondary components such as split wedges, see U.S. Pat. No. 5,391,023 to Basteck. The Basteck patent teaches “wedge means” consisting of the combination of a cylindrical stop pin and taper-headed screw. The stop pin is force fitted into the tool body and the screw engages an internal thread of the pin to draw the tapered head into the conical internal passage of the stop pin. Because the screw engages the pin, and not the tool body, the pin must be retained in the tool body by a force fit or other means independent of the screw. One drawback of this device is that as the screw is advanced in the pin, rotational and linear forces are exerted on the stop pin which over time can degrade the force fit. As the screw is advanced, the stop pin is split along the slot, each side of the stop pin moving away from its longitudinal axis. The greatest increase in diameter of the stop pin is at the top of the pin, where the screw head taper is widest, and progressively decreasing along the length of the stop pin to the end of the slot, where expansion is essentially prevented by the solid nature of the stop pin. The asymmetrical expansion of the stop pin (greater at the top than at the bottom) creates an arcing moment that is delivered to the cutting element adjacent the stop pin. A drawback of this device is that this arcing moment can cause the insert to tend to rotate in the pocket.
In another common design, one wall of the insert-receiving pocket in the tool body is replaced with a wedge-shaped member that slides along the insert flank when actuated by adjustment screws. Loosening or tightening adjustment screws produces movement of the wedge-shaped member which movement is translated into movement of the insert with respect to the tool body. Applicants have observed a number of drawbacks associated with such devices. For example, the contact between the wedge-shaped member and the tool body often results in a friction producing irregular sliding of the wedge-shaped member.
Another known design to adjust the position of an insert mounted onto a tool body provides a cantilevered wall integrally connected to the tool body, that forms a portion of the pocket that supports a side of the insert and a wedge mechanism for elastically flexing the wall to adjust the position of the insert, see U.S. Pat. No. 6,056,484. One drawback of this design is that it requires the manufacture of precision elements integral with the tool body, which is expensive and time consuming. Furthermore, the integral nature of the wall requires lengthy downtime in the event of failure or damage to the adjustment device due to the necessity to rework the tool body in the event of failure of a single cantilevered wall.
Thus, there is a need for a device for making fine adjustments to the position of cutting inserts mounted on a multiple insert tool that provides better accuracy and reliability of cutting edge position adjustment than prior art adjusting devices. There is seen a further need that such an adjustment device has parts which are quickly and easily replaced in the event of wear or failure and would require less precision tooling of the tool body to reduce the cost of the resulting adjustable multiple insert tool. It is, of course, desirable that the adjustment device is readily retrofit into conventional tools with a minimum of retooling.